This invention is in the field of printing and more specifically systems for applying ink to an applicator roll in a metering fashion. In flexographic printing, the board to be printed is passed between a rotating plate cylinder and an impression roll. The plate cylinder has mounted thereon a printing plate contactable with a third roller applying ink to the plate once per revolution of the plate cylinder. Fresh ink is continuously applied to the applicator roll with some type of device used to remove excess ink from the outer surface.
The prior applicator rolls are metal with a finely engraved outer surface provided to hold the ink upon the surface of the roll. The printing plate contacting the applicator roll is produced from rubber or photopolymer material resulting in a rapid deterioration of the printing surface. Eventually, the applicator roll which is very large and heavy must be removed from the printer and shipped back to a repair facility. The removal of the roll requires complete shutdown of the printer for several days. Once the applicator roll arrives at the repair facility, it is machined down, in certain cases recoated with metal and then engraved. The engraved surface may be as coarse as seven cells per lineal inch or a fine as five hundred cells per lineal inch. The cell is either in an inverted pyramid shape configuration with an outer square opening and a pointed base or as a quad cell configuration having an outer square opening but a reduced square base and slightly inclined walls. In either event reworking of the applicator roll is quite expensive and requires a large amount of time to repair and reinstall in the printer.
It is the practice to remove the ink from the engraved applicator roll once contacted by the printing plate by either a rubber wiper roll contacting the applicator roll or an air activated doctoring or meter blade. An expandable air tube or a series of air cylinders mounted adjacent the blade moves the blade to and from the applicator roll to remove the excess ink from the roll. The use of the rubber wiper roll with a cellular applicator roll provides an alternative method for removing excess ink from the surface of the applicator roll. Further, as the engraved applicator roll is used ink buildup along with dirt will accumulate on the roll requiring frequent cleaning of the applicator roll. Another disadvantage of the cellular applicator roll is the requirement of even ink distribution across the applicator roll to prevent the roll from burning during operation.
Disclosed herein is a printer having a rubber applicator roll with a smooth outer surface. A rod having a wire wound or similarly contoured surface is used in conjunction with a device applying ink to the applicator roll for the purpose of finely metering and removing excess ink from the applicator roll prior to ink transfer to the printing plate. The wire wound rod is small and lightweight allowing for very simple and quick removal from the printer for the purpose of installation of a new rod having a different metering capability depending upon the size of the wire wrapped thereon. The rubber applicator roll does not wear nearly as fast as the metallic cellular applicator roll. The necessity for refinishing of the applicator roll as previously described is completely eliminated. Superior printing results are achieved since the ink may be metered on the applicator roll through the use of different wire wound rods depending upon the type of printing required. For example, heavy or large lettering requires a large amount of ink on the applicator roll and thus a metering rod having a large wire wrapped thereon is utilized as compared to fine small printing in which case a metering rod having a fine wire wrapped thereon is utilized. Previously, the metallic cellular applicator roll having a fixed configuration was used for all printing including fine and large printing due to the large amount of time and effort required for the removal of the applicator roll. Thus the prior applicator rolls would be chosen to apply an average amount of ink somewhere between what was actually required for fine printing and heavy printing. The results using such an applicator roll are unsatisfactory.
The metering rod and rubber roll system disclosed herein are designed to be included as original equipment or installed into existing printers in the form of a kit. The cost of such a system is significantly lower as compared to the cellular applicator roll.
Grooved rollers have previously been used for a variety of tasks. For example, U.S. Pat. No. 3,718,117, issued to Lewicki, Jr. discloses a grooved rod used to apply a uniform coating of particulate containing material. A similar device is disclosed in U.S. Pat. No. 3,312,191, issued to Lowe. Likewise, a grooved roller for use in a rotary printing press is disclosed in U.S. Pat. No. 3,098,437, issued to Tyma, Jr., et al. whereas U.S. Pat. No. 3,613,575, issued to Kantor discloses a grooved oscillator roll for use in a printing press to achieve break up and distribution of the substances with which it comes into contact.